Very Computer

I've setup a machine using Slackware 3.5.

My machine, named mail.domain-a.com at the same time running named.
but the DNS of mail.domain-a.com is running on my ISP.
the named of mail.domain-a.com is running a domain name, domain-b.com
now domain-a.com had no problem receiving mail and sending mail.
But domain-b.com couldn't receive mail.

I've already add virtualtable on on the .m4 files and generated a new
sendmail.cf
i 've already add Cwlocalhost domain-a.com domain-b.com to sendmail.cf
and make a file /etc/relay-domain haveing domain-a.com domain-b.com.

But just couln'dt get that sendmail working.

Thanks in advance.

Best regards
Leo Wong